Abstract: To provide theoretical guidance and technical support for oat production in dry farming area, we exa-mined the effects of moisture and humic acid (HA) on the accumulation and distribution of non-structural carbohydrates (NSC) in different organs of oat, as well as the mechanism of sugar metabolism and grain weight formation of oat. Two oat cultivars, ‘Mengnong Dayan 1' and ‘Neiyan 5', were used as experimental material. HA and clean water (CK) were foliar sprayed under dry framing (without irrigation) and limited irrigation (irrigated twice at jointing and heading stage). The dynamics of NSC components in stems, leaves and panicles, as well as the changes of carbon metabolism-related enzyme activities at different growth stages of oats after flowering were measured. Results showed that the trend of the contents of NSC in stems, leaves and panicles, in both two oat cultivars increased firstly and then decreased with the prolong of post-anthesis time. The contents of NSC in different organs were similar between two oat cultivars. Under irrigation treatment, the fructan content in panicle for Mengnong Dayan 1 of HA was higher than that of CK, with magnitude of enhancement being significantly greater than that corresponding treatment under dry farming. Under irrigation condition, the fructan, invertase activities in leaves and grain weight per panicle for Mengnong Dayan 1 of HA were increased by 27.1%, 30.6% and 55.9% compared with CK, respectively. Further, the increase trend under irrigation was stronger than that under dry farming condition. For Mengnong Dayan 1, the 1000-grain weight and grain weight per panicle were positively correlated with the content of fructan in leaves. In conclusion, the synergistic effect of moisture and humic acid could effectively regulate the accumulation of oat fructans and the activities of carbon metabolic enzymes, consequently promoting the formation of yield.

Key words: water, humic acid, oat, carbohydrate, soluble sugar